This invention relates to a device which is useful for applying a uniform thickness of a spreadable coating to planar surfaces and, in particular, for applying self-levelling coatings to floors.
There are certain floor coatings which require highly specialized application techniques in order to obtain the desired surface finish and performance characteristics. Examples of such coatings are the high performance polymeric floor coating systems called "self-levelling systems".
A major problem in installing such systems is that they must be applied evenly over the surface at least to the extent that there are no puddles or excessive build-up areas, and conversely, no thin or uncoated regions. Conventional rollers or brushes are relatively ineffective with such floor coating systems because rollers and brushes do not permit the desired uniform application. Further, the application must proceed relatively quickly because such coatings routinely involve two package materials whose cure rate is rapid, thereby limiting useful working time.
Some have attempted to solve the problem by designing a notched trowel, a notched rubber squeegee, or a screed bar that is dragged through the coating to "calendar" the coating in much the same way as adhesive is spread for the installation of floor tile. However, many secondary problems result from these approaches. For example, the notched steel trowel approach places unreasonable demands on the coating's "flow out" or "self-levelling" ability with the consequence that the desired surface finish is not achieved, especially that portion of the material which is applied toward the end of the pot-life. Moreover, the device is difficult to clean, and the amount of material applied varies with angle of the trowel to the floor.
The notched rubber-squeegee approach suffers the same weakness as the steel trowel described above, and further, can yield varying results depending on pressure applied by applicator. A screed bar incorporates a multitude of spacer pins that theoretically keep the screed bar positioned uniformly above the floor surface, thereby "calendaring" a uniform layer of coating material. In reality, because the screed pins must scrape through the coating, the bar tends to leave grooves in the floor which often do not flow out uniformly, resulting in undulations in the floor. The screed bar is also difficult to clean, difficult to adjust, and performs especially poorly if the floor surface is rough. Complications can also occur when the material collects on this device and subsequently drips on the finished floor, resulting in an imperfection. A screed bar is further limited because it typically can be used in only one direction, i.e., it is not a bi-directional device.
Accordingly, it would be desireable to have a device that is useful for applying spreadable coatings on planar surface such as self-leveling coatings, and that overcomes some or all of the above disadvantages.